DESCRIPTION: (Applicant's Abstract) While the prevalence of drug abuse in the homeless population is substantial, little is known about their patterns of service utilization and the types of services used (drug abuse, housing, or substitute services), or about the outcomes resulting from these services. To address this gap, this project proposes to study a random sample of 400 homeless adult men and women over two years to identify predictors of service use and status changes in the drug abusing homeless population. Building on more than a quarter of a century of combined experience in research and service provision for the homeless population this team will test a theoretical model that predicts Service Use, Needs, Costs, and cOnsequences for the Drug Abusing homeless population (SUNCODA). The opportunity to follow a non-drug abusing homeless population comparison group will provide evidence about the impact of drug use disorders on homelessness in terms of relationships between service utilization patterns and status change (consequences). Obtaining organizational, financing, and management structure data from relevant service agencies to this population will provide the opportunity to investigate how structural characteristics of services predict actual service use by drug abusing compared to non-drug abusing homeless individuals. Finally, this study will compare costs associated with treatment of drug abusing and non-drug abusing subjects. The proposed project is particularly significant in that it directly addresses well-documented gaps in the literature on service utilization, changes in status, and costs in the drug abusing homeless population. Results from this project will have significant impact on public policy, including guidance of allocation of resources for effective service provision and informing future discussions of treatment alternatives for this particularly difficult population. The sample will be randomly selected from a variety of public settings, including overnight shelters, day centers, and specialized rehabilitation programs for homeless people, as well as from street locations. All subjects will be interviewed at baseline and at one-year intervals with an instrument adapted for this study collecting diagnostic, personal history, sociodemographic, and status data (modified for each wave). Subjects will be asked to submit a urine screen at all three waves of data collection. All subjects will be asked to provide access to their medical, psychiatric, and substance abuse records so that agencies can provide information on type and extent of service use over time. In addition, subjects will participate in quarterly reports to detail changes in functioning an service use over time. Exhaustive tracking methods will be utilized to maximize subject retention. Structural characteristics (organizational, management, and financing) data will be collected from service agencies at baseline to examine their impact on service use.